Phase shifting the circadian rhythm of neuronal activity in the isolated Aplysia eye with puromycin and cycloheximide. Electrophysiological and biochemical studies

Abstract

The effects of pulse application of puromycin (PURO) or cycloheximide (CHX) were tested on the circadian rhythm (CR) of spontaneous compound action potential (CAP) activity in the isolated Aplysia eye. CAP activity was recorded from the optic nerve in constant darkness at 15degreesC. PURO pulses (6, 12 h; 12--134 mug/ml) and CHX pulses (12 h, 500--2,000 mug/ml) caused dose-dependent phase delays in the CR when administered during projected night. PURO pulses (6 h, 125 mug/ml) caused phase advances when given during projected day and caused phase delays when given during projected night. In biochemical experiments PURO (12 h, 20 mug/ml) and CHX (12 h, 500 mug/ml) inhibited leucine incorporation into the eye by about 50%. PURO (12 h; 50, 125 mug/ml) also changed the molecular weight distribution of proteins synthesized by the eye during the pulse. The effect of PURO (12 h, 125 mug/ml) on the level of incorporation was almost completely reversible within the next 12 h but the phase-shifted eye showed an latered spectrum of proteins for up to 28 h after the pulse. In electrophysiological experiments spontaneous CAP activity and responses to light were measured before, during, and after drug treatments. In all, eight parameters in three periods were analyzed quantitatively. Of these 24 indices, only 3 showed significant changes. PURO increased spontaneous CAP frequency by 67% 0-7 h after the drug pulse and increased the CAP amplitude of the tonic light response by 23% greater than 7 h after the pulse. CHX increased the intraburst spontaneous CAP frequency by 33% during the pulse and CAP frequency of the tonic light response by 32% 0-7 h after the pulse. The above data indicate that phase-shifting doses of PURO and CHX inhibit protein synthesis in the eye without causing adverse electrophysiological effects, and suggest that protein synthesis is involved in the production of the CR of the isolated Aplysia eye.